Japanese Patent Laid Open No. 2003-75092 described below describes a unit-assembly-type heat exchanger. Fins and tubes are alternately placed in parallel to form a core. At an upper portion and a lower portion of the core, a pair of tanks are arranged, and a flow-in opening for a heat exchange medium is provided at a center of each tank.
FIG. 6 is an exploded perspective view illustrating the unit-assembly-type heat exchanger according to the Japanese Patent Laid Open No. 2003-75092. Both ends of a tube 2 are each inserted and fixed into a pair of small tanks 4 arranged at the upper portion and the lower portion, and a connection bracket 13 is arranged at a center of the small tank 4 in a longitudinal direction. Each of the connection brackets 13 is fastened with each other via an O-ring 15 and a bolt 17 to be integrated. Then, as the heat exchange medium, oil is supplied from a pipe 16 provided for the connection bracket 13 in the front row, and the oil is supplied into each tube 2 of each of units.
Next, the inventor of the present invention has already applied an oil cooler of high resistance to pressure for construction machines; Japanese Patent Application No. 2014-009616. According to that invention, a pair of cores are placed in parallel in the thickness direction thereof. In addition, flat tubes of each of the cores are inserted into a tank main body in a U-shape groove, an opening portion of the flat tube is closed with a cap member, and further both end portions thereof are closed with an end cap. Then, an opening portion is formed at a center of each tank in a longitudinal direction to bond the opening portion of the tank with that of the header by welding.